Long Term Evolution Advanced (LTE-A) system, as the standard evolution of Long Term Evolution (LTE) system, proposes enhanced Multiple Input Multiple Output (MIMO) technology, which can support a maximum of 8×8 downlink antenna configuration and improve coverage and throughput on cell edge.
LTE-A requires 4 G communication not only to meet high peak rates and large bandwidth, but also to ensure experience of users at all regions. As statistics show that 80%-90% of the throughput of the system will occur in the interior and hotspot nomadic scenarios, the interior high-speed hotspot will become more important application scenario to the mobile internet.
In wireless communication, the sender uses multiple antennas, and adopts spatial multiplexing approach to improve the transmission rate, and the receiver, such as User Terminal (UE), also uses multiple antennas. As the number of antennas increases, the channel rank also increases, and the number of layers for transmitting data also increases correspondingly. In LTE, each TB (Transport Block) can only transmit on two layers, while LTE-A supports each TB to transmit on up to four layers.
In release R10, layers 1-4 of TBS (Transport Block Size) is found by way of looking up MCS table, wherein, layer 1 TBS is jointly determined by taking ITBS (Index Transport Block Size) as index row and taking NPRB (Num Physical Resource Block) as index column. For layer 2 of TB size, i.e., TBS, when 1≦NPRB≦55, the corresponding TBS in layer 1 TBS table is found via the index (ITBS, 2·NPRB) from layer 1 TBS table, namely the value of layer 2 TBS; when 56≦NPRB≦110, NPRB and ITBS of layer 2 TBS is obtained, layer 1 TBS is found by the NPRB and ITBS, and then the sized of layer 2 TBS corresponding to layer 1 TBS is found with the conversion relation table of layers 1-2.
Before performing channel coding, the mapping of layer 1 TBS to three, layer 4 TBS carries out CRC (Cyclical Redundancy Check) treatment to the transmitted data, i.e., a number of CRC data bits are added at the tail of data to determine whether the decoded data is correct at the receiving end. When transmitting a longer TB (when transport block is longer than 6144 bits), it needs to be processed in segment, and while adding the TB CRC to the TV, CRC inspection information is respectively added on the segment-processed CB. A complete transmission block, when it is longer than 6144 bits, should include the sum of TBS+TBCRC+CBCRC, wherein TBCRC is the size of the transport block CRC, CBCRC is the size of code block CRC, so it only needs to determine the value of TBS to make a TBS table.
Determine the mapped TBS through the approximate multiple relationship of layer 1 TBS to layers 2, 3 and 4 of TBS, wherein TBS_L1 represents layer 1 TBS, TBS_LN represents n layers of mapped TBS, TB1—crc represents the TBSRC corresponding to layer 1 TBS, TBN—crc represents the TBCRC corresponding to n layers of mapped TBS, cb1—crc represents the divided CBCRC of layer 1 TBS, cbN—crc represents the CBCRC corresponding to n layers of mapped TBS, specific formula is as follows:(TBS—L1+TB1—crc+cb1—crc)×n=TBS—LN+TBN—crc+cbN—crc 
In the cell coverage area obtained by the above formula, when the TBS<299856 bits, layers 1-4 TBS try to reuse values of layers 1-4 TBS in R10, this principle will not additionally add excess TBS, so as to facilitate transmission scheduling; when TBS_LN>299856 bits, the newly increased TBS should be divisible by QPP interleaver parameters k, increasing suitability of multi-TBS, and reducing padding.
The modulation scheme in current release can not support 256 QAM, resulting in that system throughput is insufficient, and the system transmission rate can not meet the actual demand during hotspot cell coverage. Therefore, the technical problem to be solved at present has been how to optimize the current modulation scheme for the same to support 256 QAM, and improve system throughput, thus solving the problem in hotspot cell coverage of system transmission speed not capable of satisfying actual demand.